Suspension boom



E. c. WILSON 2,603,362

July 15, 1952 SUSPENSION BOOM 4 Sheets-Sheet 1 Filed D80. 51, 1948 #6 irrawir- E. C. WILSON SUSPENSION BOOM July 15, 1952 4 Sheets-Sheet 2 Filed Dec. 31, 1948 INVENTOR. Ell/.5 C. W/AJO/V ///s irrae/wy- E. C. WILSON SUSPENSION BOOM Jul 15, 1952 4 Shets-Sheet 5 Filed Dec. 51, 1948 E a "i INVENTOR. 511/5 '5; W/LSfl/V BY 7/0 irraeway- July 15, 1952 E. c. WILSON 2,603,362

SUSPENSION BOOM Filed Dec. 51, 1948 4 Sheets-Sheet 4 v INVENTOR. fizz/.5 C W/A 50A/ Patented July 15, 1952 SUSPENSION BOOM Ellis C. Wilson, Marion, Ohio, assignor to Marion Power Shovel Company, Marion, Ohio, a corporation of Ohio Application December 31, 1948, Serial No. 68,671

24 Claims. (Cl. 212-144) This invention relates to a constant tension suspension for the boom of a hoisting machine or the like, and the main object of the invention is to provide improved means for automatically preventing the sagging, or deflection, of the intermediate portion of such a boom.

A further object of the invention is to provide a suspension cable for-the intermediate portion of the boom and means for maintaining said cable under constant tension.

A further object of the invention is to provide suspension means for the intermediate portion of the boom which will be automatically maintained in substantially constant tension during the load hoistingoperation. v

A further object of the invention is to provide hydraulic mechanism for maintaining the suspension cable in constant tension.

'Afurther object of the invention is to provide a boom hoisting cable and a suspension cable which will operate simultaneously during the hoisting of the boom.

A further object of the invention is to provide suspension mechanism in which a continuous cable functions both as a boom hoisting cable and as s suspension cable for an intermediate portion of the boom.

A further object of the invention is to provide simple and efficient means for locking an intermediate portion of such a cable against movement when the bpom is in operating position.

Other objects of the invention may appear as the mechanism is described in detail.

Invthe accompanying drawings Fig. 1 is a schematicw side elevation of portions of a hoisting mechanism equipped with the invention; Fig. 2 is a schematic top plan view of the boom and a portion of the gantry of such a hoisting mechanism; Fig. '3 is a schematic layout of the cable and its connection with the various parts of the mechanism; Fig. 4 is a schematic view of a second cable and its connections with the various parts of the mechanism; Fig. 5 is a side elevation of a portion of a gantry showing parts of the mechanism mounted thereon; Fig. 6 is a side elevation of one of the locking devices; Fig. '7 is a section taken on the line '|'l of Fig; 6; Fig. 8 is a disassembled view of a device for stabilizing the cable; and Fig. 9 is a diassembled view of a stop device for locking one end of the cable against movement. I

In these drawings I have illustrated one embodiment of my invention and have shown the same as applied to the boom of an excavating machine of a well known type. It is to be understood, however, that the mechanism as a whole, as well as the several parts thereof, may take various forms and may be applied to mechanisms of various kinds without departing from the spirit of the invention.

I In the'embodiment here illustrated the excavating machine comprises a supporting structure ill, herein designatedas a platform, which is rotatably mounted on a base II which may be a part of traction mechanism on which the platform is mounted. Mounted on the platform is a gantry [2, here shown as of the A-frame type. A boom I3 is pivotally mounted at its foot on the platform H], as shown at [4. At its point the boom is provided with a sheave l5 about which extends a load hoisting cable It which is connected with a hoisting mechanism or drum I! on the platform. The boom is moved to and supported in an inclined operating position by a cable connected with the boom adjacent the point thereof and with a suitable hoisting mechanism, usually a cable drum. When a boom is supported in this manner without intermediate support the intermediate portion thereof has a tendency to sag or to be deflected due to the weight of the boom alone, and when a load is imposed on the point of the boom the latter is subjected to longitudinal compression which tends to increase the sag or deflection thereof. The booms of many hoisting mechanisms, such as large capacity excavating machines, are very long, often exceeding feet in length and the longer the boom the reater the tendency of the same to sag. The sag or deflection of the intermediate portion of a boom seriously affects the strength of the boom, especially when the latter is of substantial length. To eliminate or reduce the extent of the sagging by increasing the cross sectional dimensions of the'boom or by using heavier material in its construction increases the weight of the boom and its cost and is not a satisfactory solution of the problem. It has been proposed heretofore to provide'a supplemental support for the intermediate portion of the boom but these, for one reason or another, have not been satisfactory in use. It is, therefore, the purpose of this invention to'provide means which will satisfactorily prevent the sagging or deflection of the intermediate portion of a boom and will thereby enable theweight of the boom to be decreased or the length thereof increased without increase in the cross sectional dimensions thereof.

For that purpose I have provided a suspension cable connected with an intermediate part of the boom and means for maintaining the same in substantially constant tension sufficient to prevent sagging 0r deflection of the boom during the load hoisting operation, regardless of the load imposed onthe point thereof. Preferably this suspension cable is of such a character that it will support the intermediate portion of the boom during the hoisting of the boom to the desired inclined operative position and, in the present instance, the suspension cable is operated simultaneously with the boom hoisting cable, but it is not necessary that it should be maintained in constant tension during the hoisting of the boom as there is no load on the point of the boom at that time. When the boom is in operating position the suspension cable is anchored at one end and a constant pull is exerted on the other end thereof. Preferably, but not necessarily, the boom hoisting cable and the suspension cable constitute parts of a single continuous cable.

The boom hoisting cable I8 is connected at one end with a hoisting mechanism, such as a cable drum l9, and is connected with the boom adjacent the point of the latter, and may be reeved back and forth between the boom and the gantry as often as may be desirable in each particular installation. As here shown there is mounted on the gantry a set of sheaves including the sheaves 20, 2|, 22, 23, 24, and 25. Mounted on the boom adjacent the pointv thereof is a set of sheaves including sheaves 26, 21, 28 and 29. The cable l8 extends from the drum l9 about a sheave 30, then about sheave on the gantry to sheave 26 on the boom, then back to sheave 2| on the gantry, and then about the other sheaves on the. boom and on the gantry. After passing sheave the cable passes about a sheave 3| on one side of the gantry to a sheave 32 on the other side of the gantry. From the sheave 32 the cable passes around a guide sheave 33, then about sheaves 34 and 35 connected with an intermediate portion of the boom and preferably constituting parts of a bridle 36. From sheave 35 the cable passes about sheaves 31 and 38 to a device for exerting a constant pull on the cable and thereby maintaining it under constant tension, this device being designated as a Whole by the reference numeral 39.

Releasable mean are provided for anchoring an intermediate portion of the cable to a fixed part of the gantry at a point on that side of the bridle 36 opposite the tension maintaining device, as shown at 40. When so anchored that portion of the cable between the drum l9 and the anchoring device constitutes a boom supporting cable and is controlled solely by the drum I9, and that portion of the cable which extends from the anchoring device 40 about the sheaves 34 and 35 to the tension maintaining device 39 constitutes a boom suspension cable which may be actuated by the tension maintaining device without affecting the boom supporting portion of the cable. Preferably the boom is raised to the desired operating position before the intermediate portion-thereof is anchored at 40 and for that purpose releasable means are provided for anchoring to a fixed support that end of the cable which is connected with the tension maintaining device, as shown at 80. When the end of the cable is so anchored the cable as a whole functions as a boom hoisting cable and the suspension portion thereof supports the, intermediate portion of the boom but the tension maintaining deviceis inoperative. When the boomhas been raised tothe'desired operating position and the load hoistingoperations are to begin, the intermediate portion of the cable is anchored, at 40, and the end-of the cable'which is connected with the tension maintaining device is released for controlby that device and a constant pull is exerted on the suspension portion of the cable during the load hoisting operations to prevent the deflection of the intermediate portion ofthe boom.

On very long booms it is desirable to support the intermediate portion of the boom at two points and is also desirable to provide a second boom hoisting cable as a safety factor. Therefore in the present construction I have shown a second hoisting cable 4| connected at one end with a second boom hoisting drum 42 and reeved about a second set of sheaves on the gantry and a second set of sheaves on the boom, as shown in Figs. 1, 2 and 4. The second set of sheaves on the gantry is preferably identical in number and arrangement with those of the first set, as shown in Fig. 3, and is designated generally by the reference numeral 43. The second set of sheaves on the boom also preferably corresponds in number and arrangement to the first set of sheaves on the boom and is adjacent to the point of the boom but is spaced inwardly from the sheaves, 26 to 29, of the first set, as indicated at 44 in Figs. 1 and 2. The second cable 4| passes from the hoisting drum 42 alternately about the sheaves of the two sets of sheaves 43 and 44 and thence about sheaves 45 and 46- on the gantry to sheaves 41 and 48 connected with an intermediate portion of the boom which is spaced longitudinally from and in front of the intermediate portion of the boom with which the cable I8 is connected. From the sheave 48 the cable passes about sheaves 49 and 59 to a second tension maintaining device 5| to which the end of the cable is connected and a device 8| (Fig. 5) is provided for anchoring that end of the cable against movement. A looking, or anchoring, device 52 for the cable 4| is provided between sheaves 45 and 46 and is preferably mounted on the gantry, as will be hereinafter described. Thus the cable 4| operates in the same manner as does the cable I 8 and that portion thereof which is connected with the tension maintaining device 5| constitutes a suspension cable. In operation the hoisting drums l9 and 42 are operated simultaneously and act simultaneously on the boom to raise the same, and to support the boom in its operating position when the two drums are stationary. The pull exerted on the cable by the device 5| may be the same as the pull exerted onthe cable l8 by the device 39, but this is determined according to the weights of the intermediate portions of the boom which are supported by the respective suspension cables. The pull is sufficient to maintain the cable 4| .under tension at all times when the mechanism is in operation, and. to thus prevent sagging of that part of the boomwith which the cable4| is connected.

The pull exerting or tensionmaintaining devices may be of any suitable character which will serve to maintain the desired tension in the suspension cables, and ashere shown the two devices are identical in character, andare preferably fluid operated. In the'arrangement shown each of the tension maintaining devices, 39 and 5|, comprises a hydraulic cylinder 53 mounted on one, of the upright members of the gantry and preferably pivotally mounted thereon at its lower end, as shown at 54. A piston 55'within the cylinder is connected by a piston rod 56 with one end ofa lever 51'which is pivotally mounted between, its ends on a bracket 58 carried by the upright meniber of the gentry. The other arm of this lever is connected with the end ofthe corresponding cable, l8 or 4|, the arrangement being such. that the forward or upward movement. of the piston will cause the lever to exert-a downward pull on the cable. The connection between the lever and the cable is preferably adjustable to enable the lever to be accurately positioned and is hereshown as a turn buckle 59. Fluid under pressure is'supplied to the cylinder 53 by a variable displacement pump'fifl, preferably driven by an electriomotor 5L." The'o'utlet of this pump is connected by a conduit 62 with the lower end of the cylinder 53. This conduit is provided with a check valve 64, to prevent the escape or liquid from the cylinder in the event the pump should fail, and is also provided with a gauge 65 to indicate the pressure of the fluid the cylinder and with a pressure relief valve 63 toreturn a portion of the fluid to its source in the event the pressure in the cylinder materially exceeds the required operating pressure. The pump may be connected with any suitable source of fluid supply, such as a reservoir 66, and a second conduit 51 connected with the upper end of the cylinderserves to return to the reservoir any liquid which may seep past the piston. The pump unit which supplies liquid to the cylinder is of a known construction and it need not be here described in further detail.

When the hoisting mechanism is to be placed in operation and the angle at which the boom is to operate is known, the pressure required in the respective cylinders to prevent sag in the boom when operating at that angle is mathematically determined and the pump unit is adjusted to deliver the fluid to the cylinder at the desired pressure. When the required pressure has'been determined for any given operating angle of the boom that pressure remains constant and inasmuch as the weight of the boom does not change,

regardless of the weight of the load on the point of the boom, the tension so maintained in the suspension cables will prevent sag in the boom due to its own weight, and since the suspension cables are independent of the hoisting cables during the load hoisting operation, variations in the load on the point of the'boom in no way affects the pull on the suspension cables and sag in the boom is maintained at zero. Further, should the boom move slightly due to a stretching of the hoisting cable or cables this will not'affect the tension in the suspension cables and there will be no hinging effect at the points of attachment of the cables with-the boom.

The devices 40 and 52 for locking the intermediate portion of each cable against movement while the boom is in operating position may be of any suitable'character. Preferably each device is mounted on the gantry and is of such a character that it can be easily moved into and out of cable locking position. As best shown in Figs. 6 and '7 it comprises a base member 68 rigidly secured to the gantry, as by welding the same directly thereto or by welding it to other members 69 which in turn are welded to the gantry. Mounted on this base member is a movable member 10 of a length slightly less than the length of the base member 68, the latter being provided with end parts ll projecting therefrom between the ends of the member 10 and the fixed parts of the gantry so as to positively lock the member 10 against movement lengthwise of the member 68. The two members are provided with opposed grooves 12 to receive the cable, and the member 10 is secured to member 68 by two-series of bolts 13 which extend through alined bolt holes in the two members to clamp the same tightly against the cable. Preferably the grooves are lined with yieldable material, such'as a section of belting 14 to protect the cable against injury when it is tightly clamped between the two loading members'.1

2 The cable has a tendency to rotate about its longitudinal axis during boom hoisting and work- 'ing-ic'onditions, and the rotation of the cable rotatesthe screw. threaded member of the turn buckle with which it is connected, thereby changing the overall length of the turn buckle. To prevent this I have interposed astabilizer between each cable socket l5 and an adjacent leg of the gentry. In the form shown the stabilizer c0m-' prises two slidably connected and preferably telescopic arms 16 and H. The arm 16 is pivotally screw which is connected thereto are held against rotation but are free to move transversely asthe lever 51 moves about itspivotalaxis.

The means for anchoring the ends of the respective cables adjacent the tension maintaining devices may be of any suitable character and in the present instance each of the levers 51 is locked against movement by the cable with which itis connected. For this purpose removable stops, and BI, are inserted in the paths of parts rigid with therespective piston rods 56 to prevent the movement of the latter by its cable: As" shown in Fig. 9 each stop comprises a U-shaped structure adapted to be placed about the piston rod and having flanged ends 82 by which it may be bolted to a leg of the gantry with its upper end in the path of and'close to anut 83 which connects the piston rod with the lever 51. In the present instance a plate 84 is interposed between the flanged ends of the structure 80 and the leg of the gantry, the plate and structure being secured to the gantry by bolts 85. Thus the piston rod and the lever are locked against movement/by the cable and the latter is dead ended at its point of connection with the lever. While I have shown and describedone embodiment of my invention I wish it to be understood that I do not desire to be limited to the details thereof as various modifications may occur to a person skilled in the art.

Having now fully described my invention what I claim as new and desire to secure by Letters Patent is:

1. A boom suspension for a hoisting mechanism of the type including a'platform, a boom on said platform, and means for hoisting said boom, said suspension comprising a cable, means for connecting an intermediate portion of said cable with an intermediate portion of said boom, a supporting structure rigid with said platform, means for anchoring said cable to said structure on one side of and spaced from its point of connection with said boom, and means connected with said cable on the other side of said point of connection for maintaining said cable under substantiallyconstant tension.

2. A boom suspension for a hoisting'mecha nism of the type including a platform-abobm on said platform, and means for hoisting said boom, said suspension comprising a cable, means for connecting an intermediate portion of said cable with an intermediate portion of said boom, a supporting structure rigid with said platform, means for anchoring said cable to saidstructure on one side of and spaced from its point 01 connection with said boom,v power operated mechanism including a part connected with said suspension cable on the other side of' said point of connection and adapted to exert a pull thereon, and means for maintaining a substantially constant pressure on said part.

3. In a mechanism comprising a boom pivotally supported at its foot, a boom hoisting cable, means forconnecting said cable with said boom adjacent the point thereof, a suspension cable, means for connecting said suspension cable with an intermediate portion of said boom, means for actuating said cables simultaneously to hoist said boom, and other means for maintaining said suspension cable under substantially constant tension after said boom has been hoisted to operating position.

4. In amechanismcomprising a boom pivotally supported at its foot, a boom hoisting cable,

supported at its foot, a. boom hoisting cable,

means for connecting said cable with said boom adjacent the point thereof, a suspension cable, means for connecting said suspension cable with anintermediate portion of said boom, means for actuating said cables simultaneously to hoist said boom, means for holding one end of said suspension cable against movement while said boom is in operating position, a movable member connected with the other end' of 1 said suspension cable, and power operated means subjecting said movable member to substantially constant pressure in a direction to exert a pull on said suspension cable.

6. In a mechanism comprising a boom pivotally supported at its foot, a hoisting cable, means for connecting said cable with said boom adjacent the point thereof, a suspension cable connected with and constituting a continuation of said hoisting cable and having supporting connection with an intermediate portion of said boom, means connected with said hoisting cable for actuating both cables to hoist said boom, means for locking one end of said suspension cable against longitudinal movement after said boom has been hoisted to operative position, and means connected with the other endof saidsuspension cable for exerting a substantially constant pull thereon.

7. A boom suspension for a hoisting mechanism of the type includinga platform, a boom pivotally mounted on said platform and having a' sheave adjacent the point there'ofiand a boom hoisting mechanism, said suspension comprising sheaves, means for connecting said sheaves respectively with said platform and with an intermediate portion of said boom, a continuous cable connected at one end with said hoisting mechanism, extending about the sheaveadjacent the point of said boom, thence about a sheave on said platform and thence about a sheave connected withan intermediate portion ,of said boom, and means connectedrwith said cable beyond the last mentioned sheavefor exertinga constant pull on said cable. y

8. A boom suspension for a hoisting mechanism of the type including a platform, a boom pivotally mounted on said platform, a sheave supported on said boom adjacentthe point thereof, and a boom hoisting mechanism, saidsuspension comprising sheaves, means forconnecting said. sheaves respectively with said platform and oonnectedat one end with said form, a boom pivotallysupported on, said hoisting mechanism, extending about a sheave adjacent the point of said boom, thence about'a sheave on said platform and thence about a sheave connected with. an intermediate portion of said boom, power operated mechanism includ'- ing a movable part connected with said cable beyond the last mentioned sheave, and means for subjecting said movable part to constant pressure in a direction to exert a pull on said cable.

9. A boom suspension for a hoisting mechanism of the type including a platform, a boom pivotally mounted on said platform, a sheave supported on said" boom adjacent the point thereof, and a boom hoisting mechanism, said suspension comprising sheaves, means for connecting said sheaves respectively with said platform and with an intermediate portion of said boom, a continuous cable connected at one end with said hoisting mechanism, extending about the sheave adjacent the point of said boom, thence about a sheave on said platform and thence about a" sheave connected with an intermediate portion of said boom, means between the sheave on said platform and the sheave on said intermediate portion of said boom for locking said cable against movement, and means connected with saidcable beyond the last mentioned sheave for exerting a constant pull on said cable.

10. A boom suspension for a hoisting mecha-- nism of the type including a platform, a boom pivotally mounted on said platform, a sheave supported on said boom adjacent the point thereof; and a boom hoisting mechanism, said suspension' comprising sheaves, means for connecting said sheaves respectively with said platform and with an intermediate portion of said boom, 9. continuous cable connected at one end with said hoisting mechanism, extending about the sheave adjacent the point of said boom, thence about a sheave on said platform and thence about a sheave connected with an intermediate portion of said boom, means between the sheave on said platform and the sheave on said intermediate portion of said boom for locking said cable against movement, power operated mechanism including a movable part connected with said cable beyond the last mentioned sheave, and means for subj ectingfsaid movable part to constant pressur 'ina direction to exert a pull on said cable.

11. A boom suspension for a hoisting mechanism of the type including a platform, aboom pivotally mounted on said platform, a sheave'sup ported on said boom adjacent the point thereof, and a boom hoisting, mechanism, said suspension comprising sheaves, means for connecting said sheaves respectively with said platform and with an intermediate portion of saidboom, a continuous cable connectedat one end with said hoisting mechanism, extending about the sheave adjacent the point of said boom, thence about a sheave on said platform and thence about a sheave connectedv with an intermediate portion of said boom, means between thesheave on said platform and the sheave on said intermediate portion of said boom for locking said cable against movement, and means for maintaining constant tensionin that part of said cable which is connected with the intermediate portion of said boom, said means including a cylinder, a piston in said cylinder connected with said cable beyond th last mentioned sheave, and a variable displacement pump to continuously supply fluid to said cylinderat a predetermined pressure.

,12-, In a hoisting mechanism comprising a plat;-

Operation,

.- form, a gantry on said platform, a plurality of sheaves on the intermediate portion of said boom,

means connected with said cable beyond the last mentioned sheaves to exert a constant pull thereon, and means between two of the sheaves on said gantry for locking the intermediate portion of said cable against movement.

13. In a hoisting mechanism comprising a platform, a gantry on said platform, a boom pivotally supported at its foot on said platform, and a boom hoisting drum, a cable, means for connecting said cable with said drum and said gantry, for connecting a part thereof with said boom adjacent the point thereof and for connecting another part thereof with an intermediate portion of said boom, means connected with the last mentioned part of said cable for exerting a pull thereon, and a device mounted on a fixed support to engage an intermediate part of said cable and lock th same against movement.

. 14. In a hoisting mechanism comprising a platform, a gantry on said platform, a boom pivotally supported at its foot on said platform, and a boom hoisting drum, a cable, means for connecting said cable with said drum and said gantry, for connecting a part thereof with said boom adjacent the point thereof and for connecting another part thereof with an intermediate portion of said boom, means connected with the last mentioned part of said cable for exerting a pull thereon, and a locking device comprisingtwo parts mounted on a fixed support and on opposite sides of an intermediate portion of said cable, and means for moving one part of said device toward the otherpart thereof to clamp said cable between said parts.

'15. In a mechanism comprising a boom pivotally supported at its foot, a hoisting cable, means for connecting said cable, with said boom adjacent the point thereof, a suspension cable connected with and constituting a continuation of said hoisting cable andrhaving supporting connection with an intermediate portion of said boom, means connected with said hoisting cable for actuating both cables to hoist said boom, releasable means for locking one end of said suspension cable against movement during the boom hoisting releasable means for locking the other end of said suspension cable against movement after said boom has been moved to operating position, and means connected with the first mentioned end of said suspension cable for exerting a substantially constant pull thereon when said end thereof has been released and the last mentioned end thereof has been locked against movement.

16. A boom suspension for a hoisting mechanism of the type including a platform, a boom pivotally mounted on said platform, a sheave supported on said boom adjacent the point thereof, and a boom hoisting mechanism, said suspension comprising sheaves, means for connecting said sheaves respectively with said platform and with an intermediate portion of said boom, a continuous cable connected at one end With said hoisting mechanism, extending about a sheave adjacent the point of said boom, thence about a sheave on said platform and thence about a sheave connected with an intermediate portion of saidlboom,

means connected with said cablebeyond the last mentioned sheave for exertinga constant pull on said cable, means for locking said cable against movement at a point adjacent said pull exerting means during the boom hoisting operation, and means for locking said cable against movement at a point in advance of the sheave on said intermediate portion of said boom after the boom has been hoisted to operating position,

17. In a hoisting-mechanism comprising a platform, a boom pivotally supported on said platform, and a gantry on said platform, a plurality of sheaves on said gantry, a plurality of sheaves on said boom adjacent the point thereof, other sheaves on an intermediate portion of saidboom,

a hoisting drum supported by said platform,v a cable connected with said hoisting drum, reeved about the sheaves on said gantry and the sheaves adjacent the point of said boom and extending from one of the sheaves on said gantry about the sheaves on the intermediate portion of said boom,

releasable means beyond the last mentioned sheaves for locking the end portion of saidcable against movement by said hoisting drum, means connected with saidtcable beyond the last mentioned sheaves to exert a constant pull thereon, and means betweentwo of the sheaves on said gantry for locking an intermediate portion of said cable against movement.

' ,128. A-boom suspension for a hoisting mechanism of the type including a platform, a gantry on said platform; a boom pivotally mounted on said platform, a sheave on said boom adjacent the point thereof; and a boom hoisting mechanism, said suspension comprising sheaves, means for connecting said sheaves respectively with said gantry and with an intermediate portion of said boom, a continuous cable connected at one end with said hoisting mechanism, extending about the sheave adjacent the point'of said:boom, thence about a sheave on saidgantry and thence about a'sheave connected with an intermediate portion of said boom, means for locking theother end of said cable against movement by said boom hoisting mechanism,- means for-locking an intermediate portion of said cable against movement at a point in advance of the sheave on said intermediate portion of said. boom after said gantry and with an intermediate portion of said boom, a continuous cable connected at one end with said hoisting mechanism, extending about the sheave adjacent the point of said boom, thence about a sheave on said gantry and thence about a sheave connected with an intermediate portion of said boom, power operated mechanism including a movable part connected with said cable beyond the last mentioned sheave to exert a pull on said cable, means for locking said movable part against movement by said cable during the boom hoisting operation, and means for locking an intermediate portion of said cable against movement at a point in advance of the last mentioned sheave after said boom has been moved to operating position.

' 20. A boom suspension for a hoisting mechanism of the type including a platform, a gantry on said platform, a boom pivotally mounted on said platform, a sheave on said boom adjacent the point thereof, and a boom hoisting mechanism, said suspension comprising sheaves, means for connecting said sheaves respectively with said gantry and with an intermediate portion of said boom, a continuous'cable connected at oneend with said hoisting mechanism, extending about the sheave {adjacent the point of said boom, thence about a sheaveon said gantry and thence about asheave connected with an intermediate portion of said boom, a lever pivotallymounted on-a fixed support beyond said intermediate portion'of said boom and connected with said cable, power operated means for actuating said lever to exert a pull on-said cable, means for locking said lever against movement by said cable duringjthe boom hoisting operation, and means for locking an intermediate portion of said cable against movement at a point in advance of said last mentioned sheave aftersaid boom has been L moved to operating position. v

21. A boom suspension for a hoisting mechanism of the type including-a platform, a gantry on said platform, a boom pivotally mounted on said platform, a sheave adjacent the point of said boom, and a boom hoisting mechanism, said suspensioncomprising sheaves connected respectively with said gantry and with an intermediate portion -of said boom, a continuous cable con- 'nected atone end with said hoisting mechanism,

extending about the sheave adjacent the point 0f said boom, thence about a sheave on said gantry and thence about a sheave connected with an intermediate portion of said boom, a

leverpivotally mounted on a fixed support beyond the intermediate portion of said boom, a turn buckle connected with said lever and having a screw threaded member connected with said cable, -means for preventing the rotation of said screw threaded member by said cable, means for locking said-cableagainst longitudinal movementata point in advance of thesheave 'on said intermediate portion of said boom, and means *beyondthe last mentioned sheave for exerting a pull ,on said cable.

22. In a hoisting mechanism, a platform, a gantry; on said platform, a boom supported on said platform, two setsofisheaves on saidgantry, two sets of sheaves having supporting connection with said boom adjacent the point thereof and spaced diiferent'distances from said point, two

sets' of sheaves having supporting connection with longitudinally spaced intermediate portions of said boom, a hoisting drum on said platform, a cable having an end portion extending about :said drum, reeved about one set of sheaves adjacent'thepoint'of said boom and one set of sheaves on said gantry, and extending about one set of tension in those portions of said cables which 12 extend about the sheaves 0n the intermediate portions of said boom.

23. In a hoisting mechanism, a -platform, a gantry on said platform, a boom supported on said platform, two sets of sheaves on said gantry, two sets of sheaves having supporting connection with said boom adjacent the point thereof and spaced different distances from said point, two sets of sheaves having supporting connection with longitudinally spaced intermediate portions of said boom, a hoisting drum on said platform, a cable having an end portion extending about said drum, reeved about one set of sheaves adjacent thepoint of said boom and one set of sheaves on said gantry, and extending about one set of sheaves on an intermediate portion of said-boom. a second hoisting drum, a second cable having a portion extending about said. second drum, reeved about the second set of sheaves adjacent the point of said drum and the second set of sheaves on said gantry and extending about the secondset of sheaveson an intermediateporticn of said boom, devices between two sheaves of each set of sheaves on said gantry for locking the respective cables against movement when said boom is in operative position, fluid actuated devices connected with the respective cables beyond said intermediate sheaves for exerting a pull thereon, and means for continuously supplying fluid to said fluid operated devices at a substantially constant pressure.

24. Ina hoisting mechanism comprising aplatform, a gantry in said platform, a boom pivotally supported at its foot on said platform, and a boom hoisting drum, a cable, means for connectmediate portion of said boom, means connected with the last mentioned part of said cable for exerting a pull thereon, and a cable locking device comprising two elongate members having opposed grooves to receive said cable, one of said members being rigidly secured at its ends to spaced parts of said gantry, the other of said members being of a length less than the length of the 'first mentioned member, and clamping bolts extending through said members, said first mentioned member having at each end thereof a rigid part extending between the ends of the last mentioned member and the respective parts of said gantry to which said first mentioned member is secured, to prevent the relative longitudinal movement of said members.

ELLIS C. WILSON.

REFERENCES CITED The following references are of record in the file of this patent:

V UNITED STATES PATENTS Number 

